Topic
High harmonic generation
About: High harmonic generation is a research topic. Over the lifetime, 11694 publications have been published within this topic receiving 222650 citations. The topic is also known as: HHG.
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TL;DR: In this article, an asymptotic expression for the spectrum of spontaneous x-ray emission from an axisymmetric monoenergetic electron beam is derived and three-dimensional particle-in-cell simulations of a 25-GeV electron bunch propagating in a laser-produced ion channel are mad...
Abstract: X-ray generation by relativistic electrons in an ion channel is studied. The emission process is analyzed in the regime of high harmonic generation when the plasma wiggler strength is large. Like for the conventional free electron laser, the synchrotron-like broadband spectrum is generated in this regime. An asymptotic expression for the radiation spectrum of the spontaneous emission is derived. The radiation spectrum emitted from an axisymmetric monoenergetic electron beam is analyzed. The stimulated emission in the ion channel is studied and the gain of the ion-channel synchrotron-radiation laser is calculated. It is shown that the use of laser-produced ion channels leads to a much higher power of x-ray radiation than the one in a self-generated channel. In addition, the mean photon energy, the number of emitted photons and the brilliance of the photon beam increase dramatically. Three-dimensional particle-in-cell simulations of a 25-GeV electron bunch propagating in a laser-produced ion channel are mad...
136 citations
TL;DR: Several formal aspects of Floquet theory, including the convergence of the induced dipole moment, gauge invariance, and the normalization of the wave function are addressed, as well as the influence of resonances on the ionization rates.
Abstract: We report results of large-scale nonperturbative (Floquet) calculations of rates for harmonic generation and total ionization of H(1{ital s}) by fields whose intensity ranges from about 10{sup 12} to 3{times}10{sup 13} W/cm{sup 2} and whose wavelength ranges from 265 to 1064 nm. At long wavelengths and moderate to high intensities, perturbation theory yields estimates of total ionization rates that are orders of magnitude too large, and estimates of harmonic-generation rates that exhibit a qualitatively incorrect behavior with respect to order. We have studied the influence of resonances on the ionization rates, and we illustrate the resonance enhancement of the ionization yield for a realistic pulse. Finally, we address several formal aspects of Floquet theory, including the convergence of the induced dipole moment, gauge invariance, and the normalization of the wave function.
136 citations
TL;DR: In this article, the superposition of selected higher order harmonics and continuous background, produced in Ar gas through two time delayed 60 fs pulses at 800 nm, is measured as a function of their delay time.
Abstract: The superposition of selected higher order harmonics and continuous background, produced in Ar gas through two time delayed 60 fs pulses at 800 nm, is measured as a function of their delay time. An isolated less than 100 as sharp feature, indicative for pulse production in the attosecond regime, followed by a subfemtosecond beating, indicative for the production of trains of sub-fs XUV pulses, is clearly observable in the resulting temporal trace. The trace Fourier transforms to a frequency spectrum composed of harmonics from the selected ensemble and a continuous background that correlates with the observed ultrashort feature. Numerical simulation spectra encompass similar temporal localization.
135 citations
TL;DR: In this paper, the authors investigated the generation of high harmonics from the interaction of 150 fsec, 790 nm, and 395 nm laser pulses with solid targets, and demonstrated a strong dependence of the conversion efficiency on the temporal pulse shape and the resulting density scale length of the preformed plasma.
Abstract: We have investigated the generation of high harmonics from the interaction of 150 fsec, 790 nm, and 395 nm laser pulses with solid targets. Experiments are presented that demonstrate a strong dependence of the conversion efficiency on the temporal pulse shape and the resulting density scale length $(L/\ensuremath{\lambda})$ of the preformed plasma. The highest conversion efficiencies are achieved for short density scale lengths $(L/\ensuremath{\lambda}l~0.4),$ which result from high contrast ratio pulse interactions.
135 citations
TL;DR: In this article, the role of surface plasmon in second harmonic generation from arrays of gold nanorod particles excited by femtosecond laser pulses is investigated as a function of incident light polarization and irradiation wavelength.
Abstract: The role of surface plasmon in second harmonic generation from arrays of gold nanorod particles excited by femtosecond laser pulses is investigated as a function of incident light polarization and irradiation wavelength. In addition to photoluminescence, a peak of second harmonic is observed and is found to depend on the polarization and wavelength of the fundamental frequency laser beam. In particular, the authors found similarities between extinction spectra of the nanoparticles and spectra of emmitted second harmonic. This behavior can be explained by resonant excitation of localized surface plasmon resonances.
135 citations